The present invention relates generally to rolling apparatus including a plurality of rolling mills arranged in series for progressive rolling of wire rods, steel sections, steel bars or the like stock materials. In such rolling mill arrangement, twist roller guide devices are employed in a continuous rolling operation in which the stock being rolled is properly twisted between each two adjacent rolling mills from its state as extended out of the preceding mill so as to run into the following mill in a state raised in transverse cross section vertically or, as with the case of a stock of rectangular cross section, at an angle of inclination of 45 degrees and the guide devices are each arranged adjacent to the exit of the preceding rolling mill to receive the stock as extended therefrom and impart to the stock an angle of twist required. The present invention relates particularly to twist roller guide devices of the kind described.
Generally, in the continuous rolling operation of a set of horizontal rolling mills, it is requisite that the stock bar extended from between the working rolls of the preceding rolling mill (which will be referred to hereinafter as the first rolling mill) and having a longitudinal axis of cross section that is horizontal is twisted in order that it may be introduced into the roll nip of the second or following rolling mill with the cross-sectional axis raised to the vertical or at an angle of 45 degrees.
An advanced form of twist a roller guide device for rolling mill use includes a pair of adjustable top and bottom twist rollers which receives the stock as extended from the first rolling mill and having the longitudinal axis of cross section horizontally directed and gives to the stock a definite angle of twist to place the cross-sectional axis at a predetermined angle of inclination to the horizontal.
In operation, the steel bar or other stock received in the twist roller guide continues to advance while turning gradually in accordance with the exact angle of twist given by the paired twist rollers of the guide device and reaches the roll groove of the second rolling mill, assuming a state raised as described above at the roll nip point. With such guide devices arranged between the successive rolling mills, the stock is rolled progressively, entering each of the rolling mills stably in a definite cross-sectional attitude. This makes it possible at all times to obtain a desired high quality product having an exact reduced cross-sectional shape and area.
Such technique of twisting a stock being rolled into a raised state of cross section by use of a pair of twist rollers is generally considered highly reliable but involves some problems as described below.
In the twist roller guide device, the paired twist rollers are set an angle corresponding to the predetermined angle of twist to be given to the stock and, because of this, if the stock as extended out of the first rolling mill in a state having a horizontally directed longitudinal axis of cross section be introduced in that state into the paired twist rollers, the forward end of the stock must come into collision with the twist rollers and hence both the stock end portion and the twist rollers be heavily damaged.
To overcome this situation, it has been common practice to employ twist guide means having a guide aperture or bore defined therein to receive the stock as extended out of the first rolling mill. The guide bore has its wall surface twisted so that the stock received therein is gradually preliminarily twisted before entering into engagement with the twist rollers. As will be readily noted, a distance of stock travel exceeding a definite length is necessary for the stock to be twisted to such an extent that there is no excessive impact occuring between the twist rollers and the stock reaching the latter. On the other hand, the paired twist rollers are supported by a rigid framework so as to be able to grippingly hold the strip passing at high speed therebetween thereby to impart to the stock a predetermined amount of twist, overcoming the rigidity of the stock material. The framework is of a substantial size, including a centering grip mechanism needed for fine adjustment of the distance between the twist rollers to impart an optimum angle of twist to the stock, and is arranged to support the twist rollers at its end adjacent to the second or next following rolling mill. The framework itself is fixed on top of a firm rest bar or support bed. Since the twist guide described above and the framework supporting the paired twist rollers are arranged in series with each other, the distance between the stock exit of the first rolling mill and the paired twist rollers, that is, the axial length of the twist roller guide device used between the rolling mills tend to be relatively large.
Accordingly, in the past any rolling apparatus including a plurality of rolling mills arranged in series must as a whole have a substantially long axial length as long as if includes guide devices of the type described interposed between the rolling mills. Contrariwise, where such rolling apparatus is installed in limited space, sometimes it has been impossible to obtain between each two adjacent mills an axial distance enough to accommodate a guide device of the type described and friction guide means must be restored to at the sacrifice of the rolling accuracy of the apparatus.